The present invention relates to a system for interfacing a standard telephone set with a radio transceiver that is linked, directly or indirectly, to a local central telephone office in an overall telephone network. In particular, the present invention is adapted to interface the telephone set with a conventional cellular mobile radio transceiver that is part of an existing cellular radio system in an area.
Conventional telephone network systems typically require transmission lines or cables from a local telephone company central office to individual fixed locations, such as a home or an office. The telephone trunk lines entering the fixed location are connected to one or more individual telephone sets, of the touch-tone or pulse-dialing variety, or to a switching unit that may be coupled to a PBX or other type of internal office system network. Conventional telephone network systems suffer from the disadvantage of having to lay costly transmission lines, particularly in areas outside the largest population centers.
Another type of telephone system is a cellular mobile radio telephone system. This system provides for communication between a mobile base station, such as an automobile, and the telephone network. Such cellular radio telephone systems include a plurality of base station transmitter and receiver units carried by the automobile, with computer logic circuitry associated therewith, that provides a radio link with one or more cellular transmitter-receiver stations associated with an 800 MC fixed antenna. The cellular receiver-transmitter stations are linked to a computerized central switching center that interfaces with the local telephone network central office. Transmission between the mobile base transceiver to the cellular station or substation occurs by high speed digital communication.
The base station mobile radio units carried by the automobile typically include a transmitter, a receiver, and computer logic circuitry (hereinafter referred to collectively as the "transceiver") that is mounted in the automobile trunk. The transceiver is connected to a control head that is mounted in the passenger compartment for operation by the user. Typically, the control head includes a microphone, a speaker, and a touch pad for dialing and sending codes to the transceiver to control the transceiver. For example when a phone number is to be dialled, the user manually inputs the phone number which is then displayed and simultaneously stored in the transceiver memory. The user visually checks to see if the number to be dialed is correct and, if so, activates a SEND button for providing a send code to the transceiver to inform the transceiver that the number stored in its memory is to be digitally transmitted. The numbers to be dialed are then transmitted in a binary data stream for ultimate receipt by the telephone company central office.
The cellular-type transceiver control head interfaces with the trunk-mounted transceiver in a manner totally different from the way a standard telephone set interfaces with the telephone company telephone network. As such, a standard telephone set cannot be coupled with a conventional cellular radio transceiver since the inputs required to control the transceiver, and the transceiver outputs provided to the control head, are simply not compatible with the typical touch-tone/pulse-dialing telephone set.